Best way to keep deck posts/beams from 'racking'?

jcims · 08-24-2009, 08:02 AM

Hi folks,

Midway through my deck framing. The deck is attached to the house via ledger, is 26' long along the house and extends 20' out. Posts are 6x6 treated on an 8' grid, notched to accept 2 2x12" beams. Due to the post pattern, both beam and joist spans are 8'. Joists are 12" OC to avoid flexing in (to be installed) composite decking.

Anyway, the posts are on an inclined grade (we have a walkout basement), and range from 5' to 9' tall, and I want to put in some cross-bracing on the posts to eliminate the small amount of racking that you can feel if you go to the very extent of the joist and start rocking hard left to right.

My first thought was cables with turnbuckles in an X pattern between posts, as they could be tightened well and adjusted over time.

Second thought was 2x10's or such, also in an X pattern, fastened on the same face of the post (front or back) and bolted/lagged to the post and to each other at the intersection.

If i go the second route, would there be any problems with me using the existing carriage bolts that are used to attach the beams to the posts, or should i use dedicated fasteners? (My thought was just to reduce the number of holes in the posts to the bare minimum)

Also, if i put both members of the cross on the same side of the post, they will have to 'flex' to get past each other in the intersection, i'm assuming this is fine, and would be better than attaching them to opposite faces of the post and either using blocking to attach them to each other or just not attach them at all (afterall, you still get the 'triangle' shape if you don't attach them).

Thoughts? Am i overcomplicating?

Aggie67 · 08-24-2009, 12:23 PM

At my last house, I put up an 18x26 deck. Ledger along the house, and one row of four 8x8 piers (I could have used 6x6, but the I thought 8x8 looked more pleasing to the eye proportionally). Same deal, 2x12's on 12" centers, with composite decking. My piers were in from the end a couple feet, so it cantilevered, maybe 2-3'. And the piers were 6' oc. My basement was walk out, right smack at the midpoint of the 26' dimension. So it was a clean walkout from the back door through the two inboard piers to the back lawn. I put up 2x12 corner bracing in each pier bay, except the middle one.

So it looked like |/ \| |/ \|.

But my bracing didn't come down all that far. 2 feet maybe? And we put in a bunch of blocking. That sucker was immovable, no bounce. One summer it felt loose right after a big party, but I re-tightened the through bolts and it did the trick. I'm going back there this Friday for a party. I'll take a look and see what the dimensions were.

**Gary in WA** · 08-24-2009, 01:13 PM

Page 14: http://www.awc.org/Publications/DCA/DCA6/DCA6.pdf Covers ledgers, piers, stairs, etc.

Be safe, G